This invention relates to an ultrasonic wave transmitter for remote control systems and more particularly to a structure for the production and damping of ultrasonic waves.
Mechanical transmitters of the type which consist of a rod of a metallic material having a natural resonant frequency which transmits an ultrasonic wave by vibrating in a longitudinal mode when struck on one end thereof have been utilized for performing remote control functions in apparatus such as television receivers. To provide acceptable performance of this type of transmitter, it is essential that the rod be struck sharply enough so that the amplitude of the ultrasonic waves be large enough to actuate an associated remotely located receiver (for example, 20 to 30 feet away). Further, it is desirable that the duration of vibration of the rod be controllable by means of a damping element selectively coupled to the rod to effect an appropriate duration of signal as received by the remote control receiver. A variety of means has been used to strike and damp the rod to produce the desired result. One type of such apparatus may be found in U.S Pat. No. 3,777,700 -- Lazzery. The reduction of the complexity of components required to accomplish the aforementioned functions is desirable to reduce the cost of the transmitter without undesirably compromising its performance and reliability.